ASUS lists the ROG Strix OLED XG27AQDMG at 6.7 kg with its stand and 4.2 kg without, so 2.5 kg of what you lift from the box, more than a third, is the stand. In the monitor arm vs stock stand choice, that stand is what you are replacing, and two lines on the monitor's spec sheet say how much it already does: height adjustment and the VESA mount. A monitor whose stand only tilts gains the most from an arm. One with height, swivel and pivot already covers most of what an arm offers, and the gain shrinks to the desk space under the screen.
Where the screen should sit
Canada's federal workplace safety agency, CCOHS, puts the top of the screen no higher than eye level and the screen about 15 degrees below the horizontal line of sight. It puts the screen about an arm's length away, roughly 40 to 74 cm, and suggests a slightly lower screen for people who wear bifocal or progressive lenses. With two monitors used equally, both go at the same height and distance, edges touching or angled into a shallow curve.
A stand meets that only if it can reach the height your chair and desk call for. A tilt-only stand fixes the height wherever the maker chose, and the only remedies are a riser under the base or an arm.
Reading the stand line on a spec sheet
The Samsung Odyssey OLED G5 G50SF and the Acer KA242Y G0bi both tilt and nothing else, so the screen height is set before you unpack them. Both list a 100 x 100 mm VESA mount, which makes them the clearest candidates for an arm.
At the other end, the Dell P2425H stand adjusts for height and also swivels and pivots into portrait. On a desk with room for its base, an arm adds reach and clearance but little range of movement the stand lacks. The XG27AQDMG sits between them, with 120 mm of height travel and a tilt of 20 degrees back and 5 forward on the ASUS sheet.
The curved Dell Alienware AW3225QF has a stand that adjusts height, tilt and swivel but does not pivot, and a curved 4K panel has little reason to stand on end anyway, so an arm's rotation adds nothing there.
The VESA line and the adapters
VESA's Flat Display Mounting Interface standard defines the screw patterns on the back of a monitor, and desk monitors mostly use a 75 x 75 mm or 100 x 100 mm square. If your monitor uses the smaller one, as the Samsung Odyssey G55C does, check that the arm's plate lists it.
Apple sells the Studio Display XDR with a tilt and height stand that offers 105 mm of travel, and lists a VESA mount adapter for 100 x 100 mm mounts as a configuration option. Portrait orientation appears only under the VESA option, so a buyer who wants to rotate the screen has to choose the adapter when ordering.
The Dell U5226KW, a 51.5-inch 6K monitor, lists 100 x 100, 200 x 100 and 200 x 200 mm patterns, and a screen of that size needs an arm rated for both its width and its weight, so compare the arm's limits against Dell's figures before you order.
The weight an arm has to hold
An arm's rating applies to the screen alone, so the number to compare is the weight without stand, the 4.2 kg in the ASUS example and not the boxed weight. Gas-spring arms list a range with a minimum as well as a maximum. A screen near the bottom of the range can drift upward, and one near the top can sag, so pick an arm whose range puts your monitor near the middle.
Desk construction counts as much as the arm. A clamp needs a solid edge with clearance underneath, and glass tops, hollow-core panels and desks with a rear rail can rule it out. A grommet mount through a cable hole is the alternative. The farther the arm extends from its clamp, the more any desk wobble shows at the screen, which a short, heavy stock stand avoids.
What an arm gives back
The plain gain is the desk under the screen. A stand base takes up a patch in front of the panel, and an arm clears it for a keyboard pushed back, a laptop or a notebook. Arms with cable channels route the display and power cables along the arm, but check that your cables are long enough for the full reach before you mount.
Two monitors of different models are the other case where an arm earns its place. Two different stands have no reason to match in height, and a dual arm or two single arms line them up at the shared height the CCOHS guidance asks for.
Three lines to find before you order
Start with the height adjustment line. A no there means the screen height is fixed, and only an arm or a riser can move it. Then take the VESA pattern and the weight without stand to the arm's listing, and check that your monitor lands near the middle of its weight range. Measure the desk edge last, since the clamp decides whether any arm fits at all.
If the stand already adjusts height and the desk has room for its base, keep it. An arm would then buy clearance and little else.
